The majority of current robot designs use electric drives for joint actuation. In recent years direct drive motors have been used to achieve increased performance. Unfortunately, these motors suffer from overheating when holding or moving large loads. Often very large motors are needed to obtain a reasonable "continuous" torque rating. Large robots often use hydraulic or pneumatic drives to obtain higher powers. But these systems have slow response times and poor accuracy (except at very low speeds). It would be desirable to have a drive system which could deliver moderate power with good response and accuracy.